OK, so you're modem is a motorola chipset, so you're in an uphill battle. Conexant(Rockwell) and Lucent chipsets have a large list of drivers available but, here is a few places to start:

www.linmodems.org

www.tlpd.org ----> HOW-TO:Winmodems; HOW-TO:Modems

This list can get you started in the direction you want to go. I will tell you now, that if it is a software modem(no hardware driver), then you might want to try and sell the one you have now and get a Conexant chipset, or a Lucent Chipset modem. And also, you will probably not be able to use the speakerphone capabilites of that modem, just the regular modem features...

PM me if you need any help, I already fought this uphill battle with modems and Linux